This invention relates to a gas burner of the type used extensively in gas fired fireplaces, in decorative gas logs used in fireplaces and in certain commercial dryers, and more particularly to a burner of this type having a unitary inlet baffle and a method for constructing a burner with such baffle.
An underfed burner comprises a feed tube which provides a venturi to draw in air along with gas fuel, the feed tube being connected in communication with an elongated burner body intermediate closed ends of the body. The gas and air mix within the body and produce a flame which burns at outlet ports along the length of the body. A burner of this construction permits entrainment and mixing of the gas and air to occur totally within the burner body itself. Additional mixing space at either side of the burner is not required. The problem encountered with the conventional underfed burner design is that dynamic pressure is seen at the outlet of the feed tube, such pressure causing local disturbances and instability in the flame. The instability of the flame at the outlet of the feed tube can result in excessive carbon monoxide which is undesirable and, in the case of unvented gas fireplace logs, is particularly dangerous and undesirable. The prior art thus incorporated a baffle member positioned and welded within the burner body to disperse the pressure surge and reduce the carbon monoxide to acceptable levels.
The baffles used in the prior art generally comprise a plate with apertures, the plate being positioned within the burner body at the location where the feed tube opens into the burner body and a small distance within the body in both directions from the opening. The baffle permits the gas and air entering into the burner to be dispersed to permit mixing in a controlled manner along the length of the baffle plate and beyond toward the ends of the burner and exit the burner body at the exit ports. The pressure surge at the outlet of the feed tube thereby is substantially reduced with a corresponding reduction in local flame disturbances. However, the process of locating and welding the baffle within the burner body is difficult, labor intensive, time consuming and costly. This may be readily understood from the fact that the baffle must be held within the body of a burner which has a substantially cylindrical configuration with a diameter in the order of approximately 1.25 inch and the baffle plate must extend across the body in the area of the entry into the body by a feed tube having a diameter also in the order of approximately 1.25 inches. Not only must the baffle be held but it also must be welded in position. Accordingly, this adds to the cost of the burner and also to performance inconsistencies from burner to burner. Additionally, welding of the feed tube to the burner body is also a difficult process and requires a special drilling operation to raise an edge to aid in locating the two tubes and an upstanding surface about which a 360 degree weld is made.